Rotary cam operated microswitch terminal structure



T. J- LYELL Oct. 4,v 1966 ROTARY CAM OPERATED MIGROSWITCH TERMINAL STRUCTURE Filed NOV. 22, 1965 2 Sheets-Sheet Z INVENTOR. 717600096 d. LYELL BY 71%,, @v

H7TOQ/YQS \\\\\\Q N\\\ i United States Patent 3,277,249 ROTARY CAM OPERATED MICROSWITCH TERMINAL STRUCTURE Theodore J. Lyell, 32 Chimney Ridge Drive, Convent, NJ. Filed Nov. 22, 1965, Ser. No. 508,972 9 Claims. (Cl. 200-6) This invention relates in general to rotary switches and more particularly to a compact multiple contact rotary switch adapted to be quickly, easily, accurately and inexpensively repaired.

There are a large number and types of rotary switches known to the art. Many of these rotary switches employ a plurality of cams and a plurality of switch contacts so that the rotary switch can be designed to provide any desired switching program.

In practice, the vast bulk of the breakdowns or malfunctions of the rotary switches are due to a malfunction of one of the sets of contacts. When such malfunction occurs, one of two approaches is usually taken by repair personnel.

The first approach is to replace the entire switch. Replacing the entire switch generally requires upwards of a half hour in time. The repairman generally must go behind a panel on which the rotary switch is mounted and thus must turn off all of the voltages on the panel for safety reasons. He must then dismount the switch which involves disconnecting each of the leads to each of the active terminals on the rotary switch. He then remounts a new switch and reconnects each wire to its terminal. Rarely can this operation be performed in less than a half hour. Thus a great deal of down time is generated which, in many operations, has extremely expensive consequences. Furthermore, an entire rotary switch is replaced solely because a single set of contacts has gone bad. In addition, since rotary switches at any given installation are frequently programmed difierently from one another, a large number of spare parts have to be stocked.

The second repairmans approach is in recognition of the waste in replacing an entire rotary switch because a single set of contacts has gone bad and is also an attempt to avoid complex repair parts stocking problems. The second approach involves replacement and/or repair of the bad set of contacts. The great difficulty with this approach, and the reason it is less favored over the first approach, is that a great deal more down time is involved. In addition, this second approach requires a very skilled technician. Indeed, many rotary switches, when taken apart sufliciently to permit replacement of individual contacts, resemble nothing so much as a three dimensional jigsaw puzzle.

In connection with the complexity and difficulty of repairing rotary switches, it should be noted that as a general rule in the industry, manufacturers of rotary switches will not guarantee their operability after repair unless the switch is rebuilt at the factory. As a corollary to this, the general industry rule is that one spare is needed for each rotary switch installed in operating equipment.

In short, the present repair approach is expensive, ineificient and clumsy. Rotary switches have been employed as part of the control apparatus of expensive and complex equipment for a long period of time. A great deal has been done to improve the performance of the individual contacts and to extend their life. But, little or nothing has been done to facilitate the repair operation.

Accordingly, it is a major purpose of this invention to provide a rotary, multiple contact switch which may be quickly and simply repaired by a relatively inexpert repairman.

It is another purpose of this invention to provide a rotary, multiple contact switch which requires a very simple and inexpensive repair parts list.

It is a specific purpose of this invention to provide a rotary, multiple contact switch which requires only a single inexpensive repair part.

It is a further purpose of this invention to provide the above features in connection with a design that is both compact and easy to assemble in manufacture.

It is a further purpose of this invention to provide the above features in a design that enhances safe operation, and safety for the repairman.

Other objects and purposes of this invention will become apparent from the following detailed description and drawings in which:

FIG. 1 is a plan view of the rotary switch of this invention;

FIG. 2 is a side view of the FIG. 1 rotary switch;

FIG. 3 is a cross-sectional view along the plane 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view along the plane 4-4 of FIG. 1;

FIG. 5 is a cross-sectional view along the plane 55 of FIG. 1;

FIG. 6 is a perspective blow-up view of the FIG. 1 rotary switch showing the positions of the various parts and subassemblies when individual contact units are replaced during rotary switch repair; and

FIG. 7 is a cross-sectional view of the FIG. 6 blowup View.

As may be seen from the figures, and particularly FIGS. 1 and 6, the rotary switch 10 of this invention has a frame that includes two U-shaped metal brackets 12 (see FIG. 6). The two brackets 12 hold two terminal boards 14, which terminal boards 14 are mounted so as to be parallel to one another. The terminal boards 14 are removably held on the brackets 12 by means of a screw 16 and slot 18 arrangement.

This ability to remove the terminal boards 14 (which may most clearly be seen in FIG. 6) is an essential feature of the rotary switch 10 of this invention because it makes meaningful, from a repair point of view, the use of plug-in contact units 20 whenever a contact pair fails or otherwise malfunctions. Since each contact unit 20 does nothing more than provide a pair of contacts, each contact unit 20 is exactly the same as each other unit so that only one repair part need be kept in stock.

The rotary switch 10 includes a rotatable shaft 22 to which are attached a series of earns 24. Each cam 24 is axially positioned along the shaft 22 so as to be in position to actuate a separate one of the plug-in contact units 20. As may be seen in FIGS. 3 and 7, each cam 24 has an indent 24i in its periphery so as to change the state of the contact unit 20 whenever the indent is presented to the actuating finger 20 of the contact unit 20. In the embodiment shown, if the contact units 20 are normally closed limit switches, then the operation of the cam 24 is such as to maintain the contacts in the unit 20 open during the rotation of the cam 24 throughout its 360 cycle except when the indent 24i is presented to the actuating finger 20 Of course, the plug-in contact units 20 could be either normally open or normally closed and the cam 24 could operate by means of either an indent or a radially extending projection. One advantage of the arrangement shown is that the point in the 360 cycle of the shaft 22 at which each of the terminals 141 changes state is determined by the angular position of the cam 24 and thus it is possible to design the entire program for the rotary switch 10 with the use of only one type of cam. This greatly reduces the cost of manufacture of the rotary switch.

The frame is further constituted by two side plates 34,

and 35 which are removably connected to the terminal boards 14 by means of spring clips 36 to enclose the switch. The clips 36 permit ready manual removal of the side plates 34 or 35 when repair is desired.

An appreciation of the simplicity of maintenance afforded by the rotary switch of this invention may be obtained from a consideration of FIGS. 6 and 7 which show the components of the switch 10 in blown-up form as they would approximately appear during repair. Each set of contacts is contained in a unit which has two prongs 20p that plug into the sockets 14s on terminal board 14 and thus make electrical contact with separate terminals 141. An insulating barrier 14b may be seen between adjacent contacts to prevent sparkover.

All that is required during repair is that the operator pull off the side plate 35, which the leaf spring clips 36 will permit since the clips 36 provide a plug-in type of connection between the side plate 35 and the terminal boards 14. With the cover 35 removed, the repairman simply loosens the two screws 16 on that terminal board 14 having a defective contact and slides out the terminal board 14 from the plates 12 by sliding screw 16 along slot 18. He then unplugs the defective contact unit 20 (which is preferably a standard limit switch) and plugs in a new unit. Reassembly is as quick as disassembly. The board 14 is slid back into place by passing the screw 16 heads over the slot 18 and then tightening the screws 16 into place to provide a friction hold. The cover 35 is then snapped back into place and the switch 10 is ready for use. In this fashion, one of the major objectives of this invention is achieved which is a'ready, simple, quick and inexpensive means for replacing and/or repairing defective contacts.

One reason why the dual parallel terminal board 14 arrangement provides for compactness is that the spacing between the terminals 141 has to be a certain minimum in order to provide the voltage insulation necessary. Not only are the barriers 14b required, but NEMA has established certain standard spacings for maximum expected voltages. However, the cams 24 can be made much thinner than the required spacings between terminals 14t as well as thinner than the widths of the available limit switches. The arrangement shown permits alternate earns 24 to actuate limit switches 20 on opposite terminal boards 14 so that twice as many terminals 141 are provided than would otherwise be the case in a rotary switch of a given length.

By means of the repair procedure outlined above, a defective contact may be replaced in two or three minutes rather than requiring the half hour minimum in repair time that was hitherto necessary.

Each programmed position of the rotary switch 10 is held by a detent action as shown in FIG. 4. A pair of springs 26 engage a cam 28 which cam 28 has a series of indentations cut into it, one indentation for each rotary position which it is intended to program for the switch 10. This positioning cam 28 is mounted on the shaft 22, which shaft 22 (as may be seen in FIG. 3 and FIG. 4) has a rectangular configuration throughout the interior of the switch 10 so as to retain the cams 24 and 28 firmly thereon. One advantage of this positioning cam 28 being mounted on the shaft 22 is that the same blank may be employed in manufacturing the cam 28 as is employed to make the cams 24. The leaf springs 26 may be conveniently mounted to the brackets 12.

The latching arrangement shown in FIG. 4 has a further advantage in that the leaf springs 26 can be a single item for a whole family of rotary switches. Thus regardless of the number of positions that the cam 28 may be designed to provide, the spring 26 can be designed to be identical from one switch 10 to another. This provides for economy in manufacture and also, since a large number of rotary switches are likely to be used in a given installation, provides for economy and simplicity in storing spare parts. The same leaf spring 26 can be stored for use in repair of rotary switches 10 having a wide variety of programs.

As may be seen in FIG. 5,"a spring return feature may be incorporated in the switch 10 so that after the switch has been turned through its cycle, a spring 30 held by two stops 32, will serve to return the shaft 22 and the bank of earns 24 to its starting position.

This invention has been described in connection with one particular embodiment in order to provide a disclosure of a preferred form of the invention. It shall be understood that there are a number of variations in the embodiment disclosed that are within the scope of those skilled in this art and that may be made without departing from the invention as the invention is claimed herein.

I claim:

1. A rotary switch comprising:

(a) a frame,

(b) a terminal board removab-ly mounted in said frame, said terminal board having an outside surface with a plurality of pairs of electrical terminals and an inside surface with a plurality of sockets, each socket having openings electrically connected to a separate one of said terminals,

(c) a plurality of contact units, each of said units being removab'ly plugged into a separate pair of said sockets, each of said contact units having an actuating element facing inwardly to form a row of contact unit actuating elements,

(d) a rotary shaft having its axis deployed parallel to and spaced from said row of contact unit actuating elements, and

(e) a plurality of cams mounted on said rotary shaft to rotate with said shaft, each of said cams being longitudinally positioned along said shaft to actuate a separate one of said contact unit actuating elements.

2. The rotary switch of claim 1 wherein said removable mounting of said terminal board on said frame is by means of a screw and slot arrangement comprising:

a pair of screws on said terminal board, and a corresponding slot in said frame for each of said screws, each of said slots having a width sufficient to pass the shank of the corresponding one of said screws and being narrower than the head of said corresponding screws so that, when said screw shanks are passed into said slots and said screws are screwed tight, a friction hold will be established between said frame and said screw heads.

3. The rotary switch of claim 2 further characterized by:

a detent cam having a plurality of indentations mounted on said shaft for rotation with said shaft, and

a detent spring mounted on said frame for engagement with said indentations of said detent cam.

4. The rotary switch of claim 3 further characterized by a return spring mounted on said shaft to return said shaft to its starting position after said shaft has been rotated through a predetermined cycle.

5. A rotary switch comprising:

(a) a frame,

(b) first and second terminal boards mounted on said frame parallel to and spaced from one another, each of said terminal boards having an outside surface with a plurality of pairs of electrical terminals, each of said terminal boards having an inside surface with a plurality of pairs of sockets, each socket having openings electrically connected to a separate one of said terminals,

(c) a plurality of limit switches, each of said limit switches being removably plugged into a separate pair of said sockets, the actuating element of each of said limit switches facing inwardly to form two parallel opposed rows of limit switch actuating elements,

(d) a rotary shaft having its axis mounted parallel to J and substantially midway between said opposed rows of limit switch actuating elements, and

(e) a plurality of cams mounted on said rotary shaft to rotate with said shaft, each of said cams being longitudinally positioned along said shaft to activate a separate one of said limit switch actuating elements.

6. The rotary switch of claim 5 wherein said removable mounting of said terminal boards on said frame is by means of a screw and slot arrangement comprising:

a pair of screws on each of said terminal boards and a plurality of slots in said frame, one of said slots corresponding to each of said screws, each of said slots having a width suflicient to pass the shank of the corresponding one of said screws and being narrower than the head of said corresponding screws so that, when said screw shanks are passed into said slots and said screws are screwed tight, a friction hold will be established between said frame and said screw heads.

7. The rotary switch of claim 6 further characterized by a cover adapted to removably clip onto said terminal boards to provide a removable cover for the space between said boards on one side of said rotary switch.

8. The rotary switch of claim 7 further characterized by:

a detent cam having a plurality of indentations, said detent cam being mounted on said shaft for rotation with said shaft, and

a detent spring mounted on said frame for engagement with said detent indentations of said detent cam.

9. The rotary switch of claim 8 further characterized by a return spring mounted on said shaft to return said shaft to its starting position after said shaft has been rotated through a predetermined cycle.

References Cited by the Examiner UNITED STATES PATENTS 2,906,832 4/1959 Foster et al 200-38 2,943,161 6/1960 Fatit 200-38 3,159,771 12/ 1964 Duvall 3 17-1 13 X ROBERT K. SCHAEFER, Primary Examiner.

I. R. SCOTT, Assistant Examiner. 

1. A ROTARY SWITCH COMPRISING: (A) A FRAME, (B) A TERMINAL BOARD REMOVABLY MOUNTED IN SAID FRAME, SAID TERMINAL BOARD HAVING AN OUTSIDE SURFACE WITH A PLURALITY OF PAIRS OF ELECTRICAL TERMINALS AND AN INSIDE SURFACE WITH A PLURALITY OF SOCKETS, EACH SOCKET HAVING OPENINGS ELECTRICALLY CONNECTED TO A SEPARATE ONE OF SAID TERMINALS, (C) A PLURALITY OF CONTACT UNITS, EACH OF SAID UNITS BEING REMOVABLY PLUGGED INTO A SEPARATE PAIR OF SAID SOCKETS, EACH OF SAID CONTACT UNITS HAVING AN ACTUATING ELEMENT FACING INWARDLY TO FORM A ROW OF CONTACT UNIT ACTUATING ELEMENTS, (D) A ROTARY SHAFT HAVING ITS AXIS DEPLOYED PARALLEL TO AND SPACED FROM SAID ROW OF CONTACT UNIT ACTUATING ELEMENTS, AND (E) A PLURALITY OF CAMS MOUNTED ON SAID ROTARY SHAFT TO ROTATE WITH SAID SHAFT, EACH OF SAID CAMS BEING LONGITUDINALLY POSITIONED ALONG SAID SHAFT TO ACTUATE A SEPARATE ONE OF SAID CONTACT UNIT ACTUATING ELEMENTS. 